28template <
typename T>
void append_value(T &l,
const T &r) { l = r; }
33 l.insert(std::end(l), r.begin(), r.end());
36template <
typename K,
typename V>
39 l.insert(r.begin(), r.end());
74 option(std::string name_, T initial_value,
83 std::vector<std::string> alternate_names_,